As a representative storage device with a resistance value variable according to a flowing current, a resistance random access memory device and a fuse device are known. The resistance random access memory device is a memory device using conductivity change according to input/output of conductive ions to/from an insulating film and magnetization direction of a magnetic film, phase change of a crystal structure and the like, and is able to reversibly change a resistance value.
Meanwhile, as the fuse device, in addition to a fuse device which is burned out by laser light, for example, a fuse device that controls the resistance value by electrically melting down a fuse made of polysilicon is known (for example, see Non-patent document 1). As another example of the fuse device, a fuse device for performing data storage based on whether or not a gate oxide film of an MOS transistor is electrically broken down is known (for example, see Patent document 1). The foregoing electrically controllable fuse devices are particularly called electric fuses (eFUSE).
In the eFUSE, the occupied area and the current amount flown at the time of resistance change are larger than those of the foregoing resistance random access memory that electrically changes a resistance value. However, in the eFUSE, the configuration is simple, and almost no additional step is necessitated in the manufacturing process. Thus, it is often the case that the eFUSE is used not as a so-called general memory but as a storage for additional information. For example, the eFUSE is used for characteristics adjustment (trimming) of a semiconductor device (integrated circuit), redundant circuit selection, rewritable storage of characteristics values and other information after completing the device, and the like.
In general, a memory cell using the eFUSE is formed by serially connecting one eFUSE and one access transistor. In general, one end of a serially connected path (cell current path) between the eFUSE and the access transistor is connected to a power supply path through a bit line, and the other end of the foregoing cell current path is grounded. In the eFUSE, for example, by melting down a conductive layer and breaking down an insulating film, a resistance value is able to be incomparably changed, and thereby 1 bit data is storable. In this case, in writing operation for performing data storage by melting down the conductive layer and breaking down the insulating film, a writing power voltage (hereinafter referred to as a programming voltage) is applied to the foregoing power supply path. Thereby, though the resistance value of the eFUSE is changed from low resistance to high resistance, opposite operation is not possible.
In reading operation of storage data (information on whether a resistance value remains as the initial low resistance or has been transferred to high resistance), a reading power voltage (hereinafter referred to as a reading voltage) is applied to the foregoing power supply path. Then, the access transistor is turned ON, and size of a flowing current is converted to, for example, a voltage value, and sensing is performed.